During the transfer of a volatile liquid such as gasoline or a similar fuel from a storage facility, there may be an unsealed connection made between the disconnectable nozzle and the tank being filled. As the transfer operation progresses, residual gases as well as air contained in the tank, sometimes are displaced into the atmosphere.
Many municipalities and governmental agencies have proposed or adopted regulations intended to reduce or at least control these emissions. One method toward complying with mandated regulations is the provision of a substantially, or completely closed system between the fuel source or storage facility and the tank or tanks being filled.
Such a closed system normally includes individual conduits which carry the vaporizable fuel. The remote end of each conduit is provided with a manually operated dispensing nozzle. The nozzles are adapted to be removably positioned within the filler pipe of a receiving tank. Further, they include means to form a partially sealed engagement between the nozzle spout and the tank filler tube.
Also, in some instances, the fuel carrying system is not fully closed, but rather is controllably vented to the atmosphere. With such an arrangement, as liquid is pumped from the source, either of two eventualities could occur. If fuel leaving the storage tank or source is not immediately replaced by vapor from the tank being filled, air will be drawn into the system. On the other hand, when excessive vapors are withdrawn from the tank being filled, some vapors will have to be vented to avoid a pressure build-up.
Several embodiments of sealing arrangements have been found to be advantageous for providing the necessary partial or substantially vapor tight, yet disconnectable engagement at the nozzle spout. One method for providing the desired engagement, is to attach a cylindrical, flexible walled member such as a rubber boot or the like, to each fuel dispensing nozzle.
The boot, when properly positioned, will substantially surround the nozzle spout when the latter is registered in place. By use of such an arrangement, when a nozzle is registered in a filler pipe of the receiving tank, the walls of the flexible boot will be deflected and/or distorted. The boot will thereby define an annular vapor tight, or substantially vapor tight passage.
This type of arrangement has generally been found to be highly effective. Thus, when a fuel flow is introduced from a nozzle into a particular receiving tank, a slight pressure is produced within the tank to displace a mixture of air and fuel vapors. These displaced vapors will be urged upwardly through the annulus defined by the nozzle spout and the flexible member. Said vapors can then be transferred by way of the dispensing nozzle through a separate conduit to the fuel source, or to another reservoir for retaining the vapors.
The effectiveness of this system depends to a large degree on the mechanical compatibility of the vehicle fuel tank with the nozzle to permit a satisfactory mating relationship at their interface. If for any reason the contact edge of the nozzle boot does not engage the filler pipe, an imperfect seal arrangement is achieved and some vapor leakage can occur.
In conjunction with closed fuel systems, vacuum assist means have been devised which cause the vapor collection system to operate under a slight vacuum. Operationally, the vacuum system will function to establish a reduced pressure at the nozzle-tank filler pipe juncture to collect the displaced vapor by aspiration.
In the presently disclosed arrangement, a system is provided which incorporates a number of features which include: (1) provision for compensating for an imperfect seal at the vehicle tank-nozzle interface, (2) a vacuum assist means adapted to aid in withdrawing and collecting vapors from those vehicles being serviced, and (3) a common blower or vapor inductor system which is manifolded to a plurality of fuel dispensing units, which system will stabilize the vacuum condition at each nozzle regardless of how many of the latter are in operation at any one time.
The instant system thus provides a fuel dispensing or vehicle service facility which embodies a plurality of pumps or fuel filling units. A vapor return segment is incorporated into the fuel dispensing segment of the system.
Functionally, as a fuel transfer operation at any one or more of the several dispensers commences, a blower in the vapor segment is concurrently actuated. Fuel passing through the dispensing facility further actuates a proportioning valve which in turn regulates the vapor flow from that particular dispenser. Thereafter, the system's main blower will continuously operate to collect vapors and direct them to storage so long as any one or more of the individual proportioning valves is operable to communicate one or more of the dispensers with the vapor withdrawal system.
Toward assuring the operation of the overall system under varying circumstances, a vapor blower is provided having a capacity greatly in excess of the volume of vapor to be removed. A valved bypass conduit is provided across the vapor blower or inductor to recirculate vapors from blower discharge back through the blower's suction side. This arrangement maintains a substantially constant vacuum condition in the system, regardless of the vapor flow rate.
An object of the invention therefore is to provide a method for operating a fuel system for a multi-station fuel dispensing facility, which system embodies a dispensing nozzle adapted to removably engage a fuel receiving tank. A further object is to provide a vapor collecting method adapted to a fuel system which functions in response to the inflow of fuel to the receiving tank. A still further object is to provide a vacuum assist arrangement within a fuel system having a plurality of dispensing nozzles, which vacuum assist is adjusted in response to the flow of fuel into a tank, and which is stabilized to each of the nozzles, regardless of the number of nozzles in operation.